In the normal operation of a four-stroke cycle multi-cylinder internal combustion engine (ICE) each cylinder sequentially goes through the four strokes of intake (or induction), compression, power, and exhaust. A crankshaft is driven by pistons moving in the cylinders. A camshaft, turning in concert with the crankshaft, controls the intake and exhaust valves for each cylinder. At start up of the ICE an ignition key is turned in the ignition switch of the engine causing a starter motor to begin turning the crankshaft of the engine. The starter motor continues to turn the crankshaft until the engine reaches a minimum engine rotation measured in revolutions per minute (rpm) and until at least one cylinder has gone through the inlet, compression, power, and exhaust strokes and the ICE can power itself and maintain the minimum rpm. To understand what occurs at start up, it is necessary to consider what happened when the engine was last shut off. At shut off, the engine often turns through a few revolutions without fuel being delivered to the cylinders before the engine completely stops. When the engine does stop rotating, the cylinders may be in or partially through any one of the four strokes. Because fueling was terminated before engine rotation stopped, it is unlikely that any of the cylinders, even the cylinders that have just completed the compression stroke, will be sufficiently fueled to provide power during the first revolution(s) of the crankshaft when the engine is restarted.
The starter motor must turn the crankshaft which, in turn, causes the pistons to move up and down in the cylinders. The non-firing cylinders, those that were insufficiently fueled, cause an additional load on the starter motor. The starter motor must work against the pumping and compressing that occurs in the non-firing cylinders. This pumping and compressing, which is unavoidable in current four-stroke cycle multi-cylinder ICEs in which valve timing is controlled by the camshaft, occurs in cylinders that are left in the compression or power stroke cycles when the engine last stopped turning. Because the non-firing cylinders have insufficient fuel to combust when the engine is started again, these cylinders cannot provide power during the initial cycles, and the starter device must therefore perform extra work to crank these cylinders through wasted power and compression strokes.
Accordingly, it is desirable to have an improved method for starting a multi-cylinder internal combustion engine, and especially an improved method for starting an internal combustion engine that reduces the work that must be performed by the starter motor. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.